The present disclosure relates generally to turbofan engines and, more specifically, to systems and methods of reducing air flow separation in a turbofan engine with a bias-flow acoustic liner.
At least some known gas turbine engines, such as turbofans, include a fan, a core engine, and a power turbine. The core engine includes at least one compressor, a combustor, and a high-pressure turbine coupled together in a serial flow relationship. More specifically, the compressor and high-pressure turbine are coupled through a shaft to form a high-pressure rotor assembly. Intake air is channeled through the fan, and air entering the core engine is mixed with fuel and ignited to form a high energy gas stream. The high energy gas stream flows through the high-pressure turbine to rotatably drive the high-pressure turbine such that the shaft rotatably drives the compressor. After being discharged from the high-pressure turbine, the gas stream continues to expand as it flows through a low-pressure turbine positioned aft of the high-pressure turbine. The low-pressure turbine includes a rotor assembly coupled to a drive shaft and a fan. The low-pressure turbine rotatably drives the fan through the drive shaft.
Many modern commercial aircraft operate in high velocity crosswind conditions and low-speed operation at takeoff and landing, for example. The combination of such operating conditions can cause distortions in the intake air channeled towards the fan, which can cause flow separation at an interior surface of an engine nacelle housing. Flow separation at the interior surface of an engine nacelle housing facilitates forming rotating vortices within the engine nacelle housing, which can cause a rotating stall condition within the turbofan. At least some known engine nacelle housings are designed to mitigate flow separation within the turbofan. For example, at least some known engine nacelle housings are relatively thick and have a forward portion that extends past a forward face of the fan to restrict high velocity crosswind from distorting the flow of the intake air before entering the fan. However, further design modifications may be necessary to reduce distortions to the flow of the intake air.